biomes - university of oregon geography 11.pdf · 2005-04-20 · northern conifer forest/taiga....

Biomes

Arctic Tundra

Houghton and Skole (1990) and Schlesinger (1997)

Tundra

• Lowest diversity (# species/area) 3% worlds species

• Lowest net primary production (10-400 g/m2/yr)

• Limited harsh environment

• Growing season: 2-3 months

• Soils—permafrost, inceptisols and entisols

Tundra regions:

Climate

Mean annual Temp -20 C to -50 C

Mean annual Ppt10-50 cm

Moisture source: summer rain & thaw

• short growing season (6-10 weeks)• 2 months of continuous daylight• long, cold, dark winters

Climograph

Barrow, AlaskaElevation: 31 feet

Latitude: 71 18N Longitude: 156 47W Ft - Tundra

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Mean annual temp = -20º C to - 50 º C

Mean annual precipitation = 10 to 50 cm (mostly summer & snow melt)

Mechanical weathering poor soil development

Entisols/Inceptisolspoorly developed

Inceptisols: “embryonic” soilsEntisols: recent soils

Photo from USDA NRCS

Perennial, dark colored leaves

Lichen: symbiotic relation between algae and fungus

Colorado Rockies

Alpine Tundra•Thin soils •Different climate from Arctic Tundra•Freeze-thaw cycles operate on diurnal & seasonal cycle

Arctic Animals

Rangifer tarandus Ovibos moschatus

Ursus arctosBranta ruficollis

Arctic Tundra vs. AlpineHigh latitudes (lowlands & highlands) Mountain Tops mid and low latitudes

Large land area Small land area

Short growing season b/c of day length Short growing season b/c snow pack

Low light intensity High light intensity (especially UV)

Less precipitation Greater precipitation (as snow)

Permafrost Permafrost is rare

Human impacts in the Arctic• Warmer temperatures cause accelerated thermokarst

erosion = subsidence of terrain caused by thawing of frozen ground

• Little impact prior to 19th century. Native people maintained low population density

• Three periods of human impact in the Arctic:Early mining period (Alaska Gold Rush – 1870 to 1920s)WW II Military bases built throughout Alaska (1930s and 1940s)Oil and Natural Gas exploration (1960’s to present)

Northern Conifer Forest/Taiga

Houghton and Skole (1990) and Schlesinger (1997)

Fort Nelson, British ColumbiaElevation: 1253 feet

Latitude: 58 50N Longitude: 122 35W E - Boreal, Subartic

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Ottawa, OntarioElevation: 374 feet

Latitude: 45 19N Longitude: 075 40W Dcb - Moist Continental

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Saint John, New BrunswickElevation: 358 feet

Latitude: 45 19N Longitude: 065 53W Dcb - Moist Continental

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Climate considered “subarctic”growing season temperatures are coolannual precipitation is low (25-75 cm )

Precipitation:Continental(dry)Maritime(moist)

Temperature:Tropical (warm)Polar (cold)Arctic (very cold)

Source Regionsfor North AmericanAir Masses

Boreal Forest/Taiga

• 45 to 70 degrees Latitude• Low diversity (2-4 tree species)• NPP (400-2000 g/m2/yr)• Limited by growing season to north (3-4

months/yr); competition to south• Soil: spodosol (podzolization)

Podzolization

Moderate Precipitation

Iron rich hard pan layer

O = organicA = humus/clayE = wash out (eluviation)B = accumulation (illuviation)C = weathered bedrockR = Regolith or bedrock

General Soil horizons

Common trees of the boreal forest

Vegetation adaptations:evergreen needleafthick cuticle – xeromorphic leaves